diff --git a/test/cpp/qps/client_async.cc b/test/cpp/qps/client_async.cc
index 921836e201e..1b7a8d26b2c 100644
--- a/test/cpp/qps/client_async.cc
+++ b/test/cpp/qps/client_async.cc
@@ -62,7 +62,7 @@ typedef std::list<grpc_time> deadline_list;
 
 class ClientRpcContext {
  public:
-  ClientRpcContext(int ch) : channel_id_(ch) {}
+  explicit ClientRpcContext(int ch) : channel_id_(ch) {}
   virtual ~ClientRpcContext() {}
   // next state, return false if done. Collect stats when appropriate
   virtual bool RunNextState(bool, Histogram* hist) = 0;